Method for simulating high-temperature and high-pressure environment of alloy under radiation action based on molecular dynamics

Abstract

The invention discloses an alloy high-temperature and high-pressure environment simulation method under radiation action based on molecular dynamics, which comprises the following steps: establishing a molecular structure framework of an alloy according to a crystal structure and a lattice constant of the alloy, and setting initial parameters to construct an initial simulation model; performing relaxation operation on the molecular structure model in a high-temperature and high-pressure environment; performing irradiation damage simulation on the relaxed model based on molecular dynamics, selecting a central atom as a primary off-site atom, and setting incident energy and incident direction of the primary off-site atom to simulate atom cascade collision; keeping the incident direction unchanged, and adjusting the incident energy of the primary off-site atoms to obtain defect distribution and defect density under different energies; and analyzing the defect evolution law of the alloy in the high-temperature and high-pressure environment according to the simulation result. According to the method, the alloy material is observed from a microscopic atomic scale, so that a powerful support is provided for simulating a defect evolution process in a high-temperature and high-pressure environment and reflecting atomic collision of the alloy in a real radiation environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular dynamics microscopic calculation, and in particular relates to a method for simulating a high-temperature and high-pressure environment of an alloy under the radiation effect based on molecular dynamics. Background Art

[0002] With the continuous development of nuclear technology and materials science, improving the mechanical properties of irradiated materials is crucial to enhancing the safety and reliability of nuclear reactors and fusion reactors. Consequently, an increasing number of metal materials with excellent radiation resistance are being used in new nuclear power applications. Aluminum alloys, due to their low activation properties, excellent thermal conductivity, resistance to radiation swelling, and economical processing, are widely used as key structural materials in nuclear power equipment and working robots. However, under long-term irradiation conditions, atomic dislocations within aluminum alloys can be induced by collisions with irradiated ions, forming defects such as vacancies, interstitial atoms, and dislocation loops. These defects can lead to material hardening, embrittlement, and dimensional instability, seriously impacting the safe operation of reactors. Therefore, studying the evolution of internal defects in aluminum alloys under realistic radiation environments is of great significance for understanding the post-irradiation behavior of metals in actual nuclear power projects.

[0003] Existing research often uses irradiation experiments combined with transmission electron microscopy (TEM) to observe the defect morphology of metal materials. However, these experiments are time-consuming and costly, and it is difficult to capture the dynamic evolution of defects in the early stages of irradiation (on the picosecond scale) in real time. Molecular dynamics (MD) simulations can recreate the transient process of irradiation damage at the atomic scale.

[0004] Existing molecular dynamics research on material cascade collisions mostly focuses on simulating materials under normal temperature and pressure or high-low temperature and normal pressure environments, ignoring the high temperature and high pressure environmental conditions of materials in the actual working environment of nuclear reactors. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method for simulating the high temperature and high pressure environment of alloys under radiation based on molecular dynamics. The method simulates the defect evolution process of alloy materials under high temperature and high pressure environment by observing the alloy materials at the microscopic atomic scale, providing strong support for reflecting the atomic collisions of alloys in real radiation environment.

[0006] To achieve the above objectives, the present invention provides a method for simulating a high-temperature and high-pressure environment of an alloy under radiation based on molecular dynamics, comprising:

[0007] According to the crystal structure and lattice constant of the alloy, the molecular structure framework of the alloy is established, and the initial parameters are set to construct the initial simulation model;

[0008] Perform relaxation operations on the molecular structure model under high temperature and high pressure environment;

[0009] Based on molecular dynamics, the radiation damage simulation of the relaxed model is performed. The central atom is selected as the primary delocalized atom, and its incident energy and direction are set to simulate atomic cascade collisions.

[0010] Keeping the incident direction unchanged, adjusting the incident energy of the primary dissociated atoms, the defect distribution and defect density at different energies are obtained;

[0011] Based on the simulation results, the defect evolution law of the alloy under high temperature and high pressure environment is analyzed.

[0012] Optionally, the initial parameters include the spatial dimension of the molecular structure model, system composition, boundary conditions and interatomic potential function.

[0013] Optionally, the relaxation operation under the high temperature and high pressure environment is performed using an NPT ensemble with equal particle number, equal pressure and equal temperature.

[0014] Optionally, the temperature of the NPT ensemble is adjusted using the Nosé-Hoover heat bath method, and the pressure is adjusted using the Berendsen method.

[0015] Optionally, the radiation damage simulation uses an NVE ensemble with equal particle number, equal volume, and equal energy.

[0016] Optionally, the incident energy of the primary ex-situ atoms is set to 1 keV to 20 keV.

[0017] Optionally, the defect distribution and defect density are identified using a Wigner-Seitz cell method.

[0018] Optionally, the alloy is an aluminum-magnesium alloy, and its lattice structure is face-centered cubic, and the lattice constant is

[0019] Technical Effects of the Invention: The present invention discloses a method for simulating a high-temperature and high-pressure environment of an alloy under the action of radiation based on molecular dynamics. Through molecular dynamics (MD) simulation, the microstructural evolution of the alloy under the coupled action of high temperature, high pressure and radiation can be analyzed at the atomic level, achieving dynamic simulation of complex working conditions, breaking through the limitations of experiments in time, space, and efficiency, while avoiding the difficulties in handling radioactive materials. In addition, through molecular dynamics in a high-temperature and high-pressure simulation environment, different energies of radiation are applied to the alloy, and the defect evolution process of the alloy after the multiple effects of high temperature, high pressure and radiation is observed, providing significant support for the radiation resistance of service metals under actual working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0021] Figure 1 This is a flow chart of a method for simulating a high-temperature and high-pressure environment of an alloy under radiation based on molecular dynamics according to an embodiment of the present invention;

[0022] Figure 2 This is a microscopic molecular structure model diagram of the aluminum alloy according to an embodiment of the present invention;

[0023] Figure 3 The temperature cloud map of the molecular structure model of the embodiment of the present invention;

[0024] Figure 4 Graph showing the change of Frenkel pairs over time at different PKA energies according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0027] like Figure 1 As shown, this embodiment provides a method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics, comprising:

[0028] S1. Based on the crystal structure characteristics and lattice parameters of multi-component alloys, a large-scale atomic and molecular parallel simulator (LAMMPS) is used to construct microstructure models of multiple multi-component alloys. First, the research atomic species in the target alloy is selected, and the component control is achieved by adjusting the content of the atom in each model. The present invention simulates aluminum-magnesium alloys as test objects. The specific modeling method includes two core steps: (1) Initial model construction: According to the crystal type and lattice constant of aluminum, a benchmark model containing only a single atomic species is first generated; (2) Atom replacement: Using a random replacement algorithm, magnesium atoms are introduced into the benchmark model according to a preset ratio, and finally a microscopic molecular structure model containing multiple atoms is formed;

[0029] S2. Initialize the key parameters of each microstructure model, including the spatial dimensions, system composition, boundary condition settings, and the potential function for studying the interactions between atoms in the model; and construct a molecular radiation simulation model based on these parameters.

[0030] S3. Stabilize the energy of the molecular radiation simulation model and use the conjugate gradient algorithm to minimize the energy to eliminate atomic overlap and large atomic forces;

[0031] S4. Relax the energy-minimized molecular model in an isothermal and isobaric NPT ensemble with equal particle number (N), equal pressure (P), and equal temperature (T). Set the ensemble temperature, temperature-adjusted damping coefficient, pressure, pressure-adjusted damping coefficient, relaxation step length, and number of steps. Use a Nosé-Hoover thermal bath to adjust the temperature, and introduce an additional "thermal bath degree of freedom" ξ to adjust the system kinetic energy. Use the Berendsen method to control the adjustment of the system volume with pressure. The specific formula is:

[0032] Nosé-Hoover:

[0033]

[0034] Where p i represents atomic momentum, ξ represents the heat bath variable, Q T represents the inertia parameter of the heat bath (determines the temperature adjustment speed), g represents the number of degrees of freedom of the system, k B represents the Boltzmann constant, T represents the target temperature;

[0035] Berendsen:

[0036]

[0037] Where V represents the model volume, η represents the pressure bath variable, and Q P represents the pressure bath inertia parameter, P represents the instantaneous pressure of the system, and P0 represents the target pressure;

[0038] S5. Primary Dissociated Atom (PKA) settings: select the central atom of the model as the primary dissociated atom, assign it an initial motion direction and energy, and calculate the corresponding initial velocity based on the energy.

[0039] S6. Cascade collision dynamics simulation: Run a radiation cascade collision simulation in a microcanonical NVE ensemble with equal particle number (N), equal volume (V), and equal energy (E). Set the simulation step size and simulation time, turn off temperature control to observe the actual energy transfer, record atomic trajectories, and track the displacement of out-of-place atoms.

[0040] S7. Based on the simulation results of the radiation molecular simulation model under the combined action of high temperature and high pressure, the relationship between the alloy of primary dissociated atoms with different incident energies and the number of defect pairs generated is obtained.

[0041] The following molecular dynamics simulation calculation example of aluminum-magnesium alloy radiation damage test will be used to specifically illustrate the molecular dynamics-based simulation method of high-temperature and high-pressure environment of alloys under radiation, including:

[0042] S1. Use lammps software to build a microscopic molecular structure model of aluminum-magnesium alloy and define the lattice structure FCC (Face-centered Cubic) and lattice constant The model size is set to 30a×30a×30a, and 1% of the aluminum atoms are randomly replaced by magnesium atoms through the random replacement command, thereby obtaining the initial microscopic molecular structure model of the aluminum-magnesium alloy, as shown in Figure 2 As shown;

[0043] S2. Initialize the key parameters of each microstructure model. Set the model unit system to metal, the spatial dimension to three-dimensional, the boundary condition to three-dimensional periodic boundary condition, the atom type to atomic, and the potential function to the embedded atom method (EAM).

[0044] S3. Minimize the energy of the microscopic molecular structure model after initialization parameters, and use the conjugate gradient algorithm (min_style cg) to eliminate overlapping atoms and internal stress in the initialized structure model, so that the overall model tends to equilibrium and stability;

[0045] S4. Relax the energy-minimized molecular model in an isothermal and isobaric NPT ensemble with equal particle number (N), equal pressure (P), and equal temperature (T). Set the ensemble temperature to 600 K, the temperature adjustment damping coefficient to 0, the initial and final pressures in the three directions of the model to 15 MPa, the pressure adjustment damping coefficient to 1.0, the time step of the relaxation process to 0.001 ps, and the relaxation time to 50,000 steps. The entire relaxation time is 50 ps according to the relaxation time step.

[0046] S5. Primary detached atom (PKA) settings: select the atom at the center of the model as the primary detached atom, set its initial motion direction to

[135] , and set the incident energy to 1keV, 10keV, and 20keV. This atom will drive the subsequent cascade collisions.

[0047] S6. Perform cascade collision dynamics simulations on the molecular structure model of the selected PKA after high-temperature and high-pressure relaxation. Run the radiation cascade collision simulation in a microcanonical NVE ensemble with equal particle number (N), equal volume (V), and equal energy (E). Set the simulation time step to dynamically change with the distance of atomic position movement, set the atomic movement distance within a time step to no more than 0.005 times the lattice constant, set the simulation time to 50,000 ps, ​​turn off temperature control to observe the actual energy transfer, record the atomic trajectories, and track the displacement of the out-of-situ atoms.

[0048] S7. Save and output the molecular structure model after the entire relaxation and cascade collision, according to the simulation results of the radiation molecular simulation model under the combined action of high temperature and high pressure (such as Figure 3 As shown in the figure, the simulation time, simulation temperature, simulation energy, coordinate position of the xyz axis of the atom, and atomic kinetic energy are output every 1000 time steps. The exported model information is imported into OVITO to realize the dynamic display and marking of the atomic position changes of the molecular structure model under the radiation operation in a high temperature and high pressure environment. Through the Wigner-Seitz cell method, the time evolution curve of the vacancy number (Frenkel defect pair) generated by the model in the cascade collision process of radiation is output, as shown in the figure. Figure 4 shown.

[0049] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for simulating high temperature and high pressure environment of alloys under radiation based on molecular dynamics, characterized in that: include: According to the crystal structure and lattice constant of the alloy, the molecular structure framework of the alloy is established, and the initial parameters are set to construct the initial simulation model; Perform relaxation operations on the molecular structure model under high temperature and high pressure environment; The radiation damage simulation of the relaxed model was performed based on molecular dynamics. The central atom was selected as the primary delocalized atom, and its incident energy and direction were set to simulate atomic cascade collisions. Keeping the incident direction unchanged, adjusting the incident energy of the primary dissociated atoms, the defect distribution and defect density at different energies are obtained; Based on the simulation results, the defect evolution law of the alloy under high temperature and high pressure environment is analyzed.

2. The method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics according to claim 1, wherein: The initial parameters include the spatial dimension of the molecular structure model, system composition, boundary conditions and interatomic potential function.

3. The method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics according to claim 1, wherein: The relaxation operation under the high temperature and high pressure environment is performed using an NPT ensemble with equal particle number, equal pressure and equal temperature.

4. The method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics according to claim 3, characterized in that: The temperature of the NPT ensemble was adjusted using the Nosé-Hoover heat bath method, and the pressure was adjusted using the Berendsen method.

5. The method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics according to claim 1, wherein: The radiation damage simulation adopts an NVE ensemble with equal particle number, equal volume and equal energy.

6. The method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics according to claim 1, wherein: The incident energy of the primary ex-situ atoms is set to 1 keV to 20 keV.

7. The method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics according to claim 1, wherein: The defect distribution and defect density are identified using the Wigner-Seitz cell method.

8. The method for simulating a high temperature and high pressure environment of an alloy under radiation based on molecular dynamics according to claim 1, wherein: The alloy is an aluminum-magnesium alloy, and its lattice structure is face-centered cubic, and the lattice constant is

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